The long-term objectives are a molecular picture of the life-cycle of bacteriophage 2 and the use of this information to help understand general features of DNA transactions in prokaryotes and eukaryotes. The major specific aims for this grant period focus on understanding two aspects of viral growth: (1) The switch between the lytic and lysogenic pathways of phage development; (2) initiation and regulation of DNA replication. In addition, the insights and techniques developed in the lambda work will be used to learn something about complex transcriptional regulation, heat shock, and protein turnover in E. coli and about interactions at replication forks in E. coli and the eukaryotic virus SV40. Knowledge about a switch between temporal pathways is likely to be useful in understanding normal and abnormal development in humans. Regulation of DNA replication has relevance to understanding the uncontrolled growth of malignant cells. The work on the switch between lysis and lysogeny will concentrate on biochemical mechanisms responsible for the regulated turnover of lambda cII protein, which appears to be the major feature controlling the choice of pathways. The proteolytic reaction and its regulation will be investigated with purified proteins. For DNA replication, experiments will focus on the nucleoprotein assembly and disassembly reactions at the lambda origin that control the route to bidirectional replication and on the chain growth complex at the replication fork. The disassembly reaction is carried out by the heat shock proteins DnaJ and DnaK, and so the replication fork. The disassembly reaction is carried out by the heat shock proteins DnaJ and DnaK, and so the replication system provides a way to learn about the cellular role of the heat shock response. Other experiments will seek to understand in detail two transcriptional regulatory systems that may involve DNA-wound nucleoprotein complexes: galactose and ammonia assimilation (glnA).